KR100575499B1 - Beam-splitter optics design that maintains an unflipped unmirrored image for a catadioptric lithographic system - Google Patents

Abstract

The present invention relates to a refraction refractive system having a reticle optical group, a beam splitter, an aspheric mirror, a baffle plate, a folding mirror and a semiconductor wafer optical group. The reticle optical group, the beam splitter, and the semiconductor wafer optical group are disposed on the same beam axis and are different from the aspherical mirror and the folding mirror axis. Light passes through the image pattern on the reticle and is reflected by the beam splitter to the aspherical mirror. The aspheric mirror reflects light back through the beam splitter to the folding mirror. The folding mirror reflects light back to the beam splitter. The beam splitter reflects light to the semiconductor wafer optical group. The plurality of quarter phase plates may be disposed in the optical path between the optical elements of the present invention to change the polarization of the incident light. Before light passes through the semiconductor wafer optical group, any background scattered light generated by internal reflections in the beam splitter through the baffle plate is prevented from entering the semiconductor wafer optical group. In another embodiment, a spacer plate is inserted into the beam splitter. The spacer plate creates an offset between the reticle optical group beam axis and the semiconductor wafer optical group beam axis. This reduces the direct passage of light from the reticle optical group to the semiconductor optical group.

Reticle Optical Group, Beam Splitter, Aspheric Mirror, Baffle Plate, Refractive Lithography System

Description

BEAM-SPLITTER OPTICS DESIGN THAT MAINTAINS AN UNFLIPPED (UNMIRRORED) IMAGE FOR A CATADIOPTRIC LITHOGRAPHIC SYSTEM}

1 illustrates a system in which embodiments of the present invention may be implemented.

2A illustrates one embodiment of the present invention showing a beam splitter cube without a spacer plate.

FIG. 2B illustrates one embodiment of the present invention showing a beam splitter cube with a spacer plate. FIG.

FIG. 3A is a view showing a movement path of a light beam of the embodiment of the present invention shown in FIG. 2A;

FIG. 3B is a view showing a movement path of a light beam of the embodiment of the present invention shown in FIG. 2B;

4 shows an embodiment of a baffle plate of the present invention.

* Description of the symbols for the main parts of the drawings *

200: refraction system

210: reticle optical group

220: beam splitter

225: folding mirror

230: aspherical mirror optical group

240: wafer optical group

250: baffle plate

The present invention relates to improved lithography systems and methods. In particular, the present invention relates to lithographic systems and methods using catadioptric exposure optics for projecting high precision images without image flipping.

Lithography is a process used to create features on the surface of a substrate. Such substrates may include those used in the manufacture of flat panel displays, circuit boards, various integrated circuits, and the like. The substrate mainly used for this application is a semiconductor wafer. Although the present description uses semiconductor wafers for illustration, those skilled in the art will also appreciate that the present description can also be applied to other types of substrates known to those skilled in the art. During lithography, the wafer disposed on the wafer stage is exposed in an image projected onto the surface of the wafer by exposure optics disposed in the lithographic apparatus. An image refers to a circle or original to be exposed. The projected image refers to the image that actually contacts the surface of the wafer. Although exposure optics are used for photolithography, other types of exposure apparatus may be used depending on the particular application. For example, each of the x-rays or photon lithography may require another exposure apparatus, as known to those skilled in the art. Specific examples of photolithography are discussed herein for illustrative purposes only.

The projected image results in a change in the properties of the layer, for example photoresist, deposited on the surface of the wafer. These changes correspond to the shape projected onto the wafer during exposure. After exposure, the layer is etched to produce a patterned layer. The pattern corresponds to the shape projected onto the wafer during exposure. This patterned layer is then used to remove exposed portions of the underlying structural layer in the wafer, such as conductive layers, semiconductor layers, or insulating layers. This process is then repeated with other processes until the desired shape is formed on the surface of the wafer.

Step-and-scan technology works in conjunction with projection optics systems with narrow imaging slots. Rather than expose the entire wafer at one time, individual fields are scanned onto the wafer one at a time. This is accomplished by simultaneously moving the wafer and the reticle such that the imaging slot moves across the field during the scan. The wafer stage must then be asynchronously stepped between field exposures so that copies of the plurality of reticle patterns are exposed across the wafer surface. In this way, the quality of the image projected on the wafer is maximized.                         

The exposure optics comprise refractive and / or reflective elements, ie lenses and / or mirrors. In general, most exposure optics used for commercial manufacturing consist solely of lenses. However, the use of reflective refraction (ie, a combination of refractive and reflective elements) exposure optical systems is increasing. The use of refractive and reflective elements allows many lithographic parameters to be controlled during manufacturing. However, the use of mirrors can cause image flip problems.

There is a need for optical system designs that can produce images that are not flipped (mirroring) on a semiconductor wafer. In addition, the optical system must be compatible with the reticle design of the previous refraction system. Finally, there is a need for optical system designs that are capable of uniform and symmetrical heat distribution to reduce the burden on the thermal compensation system.

Summary of the Invention

The present invention relates to a refractive index lithography exposure apparatus for forming an image pattern on a semiconductor wafer. In particular, the present invention is a refraction lithography system that includes a reticle optical group, a beam splitter, an aspheric mirror optical group, a folding mirror, and a semiconductor wafer optical group. The light beam is transmitted to the beam splitter cube through an image pattern formed on the reticle and reflected by the aspherical mirror. The aspherical mirror reflects the light beam back through the beam splitter cube. A quarter wave plate disposed in the optical path between the aspheric mirror and the beam splitter cube changes the polarization of the light incident on the beam splitter cube. After passing through the beam splitter cube, the folding mirror disposed adjacent to the beam splitter cube reflects the light beam. Another quarter phase plate disposed in the optical path between the folding mirror and the beam splitter cube changes the polarization of the light incident on the beam splitter cube. The light beam is then reflected onto the wafer optical group by the beam splitter cube. The wafer optical group enlarges, focuses, and / or aligns the light beam to form a pattern on the semiconductor wafer. The pattern on the semiconductor wafer corresponds to the image pattern on the reticle.

In one embodiment of the invention, a baffle plate is inserted between the beam splitter cube and the wafer optical group. The baffle plate absorbs background scattered light generated as a result of internal reflection in the beam splitter cube. Background scattered light is generated as a result of the light beam passing through the beam splitter cube and reflecting off the beam splitter cube surface. In addition, the baffle plate absorbs almost no background scattered light and reflects it into the beam splitter cube. The baffle plate also includes an opague shield that reduces the effects of light deflection on the system.

In another embodiment of the invention, the beam splitter cube comprises two optical prism halves separated by spacer plates. The width of the spacer plate is a variable of the offset created between the image axis of the object plane beam and the wafer plane beam. The object plane beam passes through the reticle group of optics from the object plane. The wafer planar beam passes through the wafer group. The width of the spacer plate depends on the desired offset amount between the image plane of the object plane beam and the wafer plane beam. The width may be zero in one embodiment (ie, the optical surface of two optical prisms halves are in optical contact) or may be changed in other embodiments. The width of the spacer plate determines the amount of background scattered light incident on the baffle plate and the wafer group. The spacer plate may be made of an optical material similar to the optical prism half of the beam splitter cube. In another embodiment, the beam splitter cube also includes two optical prism halves separated by a plurality of spacer plates. The plurality of spacer plates corrects birefringence more efficiently.

The systems and methods of the present invention provide a relatively uniform heat distribution. By allowing double passage through the beam splitter cube, the present invention symmetrically distributes the heat generated as light passes through the system. This reduces the burden on the thermal compensation system.

In addition, using the systems and methods of the present invention, the light passing through the reticle optical group is folded evenly. This prevents improper flip image formation on the semiconductor wafer without causing image mirroring.

Other features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in more detail below with reference to the accompanying drawings.

The accompanying drawings, which are incorporated herein and form part of this specification, illustrate the invention, illustrate the principles of the invention in conjunction with the description, and enable one of ordinary skill in the art to make and use the invention.

The invention will be described with reference to the accompanying drawings. In the drawings, like reference numerals refer to the same or functionally similar elements. Further, the leftmost digit of the reference number indicates the figure in which the reference number first appears.

Table of contents

1. Overview

2. Jargon

3. Beam splitter optics design

a. Beam splitter optics design without spacer plate

b. Image path in beam splitter optics design without spacer plate

c. Beam splitter optics design with spacer plate

d. Image path in beam splitter optics design with spacer plate

4. Conclusion

While the invention has been described with reference to exemplary embodiments for particular applications, it should be understood that the invention is not so limited. Those skilled in the art close to the techniques provided herein will recognize further modifications, applications, and embodiments within the scope and further fields in which the present invention is very useful.

1. Overview

The present invention relates to a lithographic system and method using refractive exposure optics for projecting a high quality image without image flips. The present invention allows for more efficient and timely generation of semiconductors.

1 illustrates an example environment in which the present invention may be implemented. A system 100 is shown that expands light 102 emitted from a light source (eg, a laser) 104 and substantially eliminates speckle patterns without changing the spatial coherence of light 102. 1 is shown. The laser 104 may be an excimer, a deep UV excimer laser, or the like. Light 102 is received by beam conditioner 108. The beam conditioner 108 outputs light to the illumination optics 110 to transmit light through the mask or reticle 112 onto the substrate 116 via the projection optics 114. One embodiment of this system may be a lithography system or the like.

2. Jargon

To explain the invention more clearly, the following term definitions will be adhered to as consistently as possible throughout this specification.

An "aspheric mirror" is a mirror having an aspheric surface. The aspherical surface of the mirror is used in a catadioptric optical system to precede or retard an incident electromagnetic energy wavefront with respect to the reflective behavior of the spherical surface.

A "beam splitter" is an optical device that splits a beam into two or more separate beams. A simple beam splitter may be a very thin sheet of glass inserted into a beam at an angle that causes part of the beam to divert in another direction. More complex types consist of two right-angled prisms coupled together in their hypotenuse. The bonded side of one prism is coated with a metal or dielectric layer having the desired reflective properties at a ratio of reflection and desired color, before being bonded. In color television cameras, for example, a three-way beam split is disposed on the interface, converting red and green light into two beacons and passing a blue image through a third vidicon tube. Three-way beam splitting prism is used. In a lithography system, the beam splitter can pass light having the same polarity as the beam splitter and reflect light having a different polarity than the beam splitter.

By "catadioptric optical system" is meant an optical system in which focal power is achieved using reflection and refraction. Although the relative power of the lenses and mirrors of a refraction optical system varies from system to system, such systems typically use a reflective surface in combination with a zero or nearly zero focusing power refractive surface to achieve a significant amount of system focus. It is characterized by gaining ability. These systems produce images that improve aberrational characteristics.

An "intermediate image" is an image formed before the final focal plane of the optical system.

A "quarter wave plate" is made of a double-refracting crystal having a thickness and a refractive index difference formed between normal alc abnormal elements through which a quarter period of phase difference passes light. Plate.

A "reticle" is an optical element located in the image plane that contains a pattern that directs the instrument and helps to measure target properties. This can be as simple as a pair of intersecting lines or a composite pattern. In semiconductor pattern generation, it is a glass or quartz substrate that contains the image of the integrated circuit.

A "wafer" is a sectional slice cut from an ingot of single crystal, fuse, polycrystalline, amorphous material having a refined surface that is wrapped or polished. Wafers are used as substrates or optics for manufacturing electronic devices. Typically, wafers are made of silicon, quartz, gallium, arsenide or indium phosphide. The terms "wafer" and "substrate" are used interchangeably herein.

3. Beam splitter optics design

a. Beam splitter optics design without spacer plate

2A shows an embodiment of the present invention having a beam splitter cube without a spacer plate. 2b shows another embodiment of the present invention having a beam splitter cube with a spacer plate. FIG. 3A shows the travel path of the light beam of the FIG. 2A embodiment. 3B shows the light beam travel path of the FIG. 2B embodiment.

2A illustrates a reflective refractive system 200 in accordance with an embodiment of the present invention. Reflective refraction system 200 includes reticle optical group 210, beam splitter 220, aspheric mirror optical group 230, folding mirror 225, baffle plate 250, wafer optical group 240 and It has a plurality of quarter phase plates 202 (a, b, c, d).

The reticle optical group 210 is adjacent to the beam splitter cube 220. Wafer optical group 240 is also adjacent to beam splitter cube 220. The reticle optical group 220 is opposite the wafer optical group 240 such that the beam splitter cube 220 separates the reticle optical group 210 and the wafer optical group 240.

Aspheric mirror optical group 230 is adjacent to beam splitter cube 220. Folding mirror 225 is also adjacent to beam splitter cube 220. Aspheric mirror optical group 230 is opposite folding mirror 225 such that beam splitter cube 220 separates aspheric mirror optical group 230 and folding mirror 225. As shown in FIG. 2A, the reticle optical group 210 and wafer optical group 240 are on the same optical axis. In addition, the aspherical mirror optical group 230 and the folding mirror 225 are on the same optical axis. However, the optical axes of the reticle optical group 210 and the wafer optical group 240 may be different from the optical axes of the aspheric mirror optical group 230 and the folding mirror 225 (see FIG. 3A). It will be apparent to one skilled in the art that other configurations of each optical object of the refraction index system 200 are possible.

The reticle optical group 210 includes a reticle 201, a quarter phase plate 202a and a reticle lens 203. The quarter phase plate 202a is disposed between the reticle 201 and the reticle lens 203. The reticle lens 203 is adjacent to the beam splitter cube 220. In one embodiment, the reticle lens 203 may have a positive or negative refractive power.

The aspheric mirror optical group 230 includes an aspherical mirror 231, a first aspherical mirror lens 232 and a second aspherical mirror lens 233. The first aspherical mirror lens 232 is between the aspherical mirror 231 and the second aspherical mirror lens 233. In one embodiment, the first aspherical mirror lens 232 has a positive refractive power and the second aspheric mirror lens 233 has a negative refractive power. The quarter phase plate 202b separates the aspheric mirror optical group 230 and the beam splitter cube 220. The quarter phase plate 202b is adjacent to the second aspherical mirror lens 233 and the beam splitter cube 220. In one embodiment, the aspherical mirror 231 is a concave mirror.

The quarter phase plate 202d separates the folding mirror 225 and the beam splitter cube 220. In one embodiment, the folding mirror 225 is a flat mirror. In another embodiment, the folding mirror is a mirror with optical power.

Wafer optical group 240 has a plurality of wafer group lenses 242 (a, b, ..., m). Wafer group lenses 242 (a, b, ..., m) are disposed between the semiconductor wafer 241 and the beam splitter cube 220. In one embodiment, wafer group lenses 242 (a, b, ..., m) have different refractive power. That is, some wafer group lenses have positive refractive power and some wafer group lenses have negative refractive power. For example, wafer group lens 242a has positive refractive power, and wafer group lens 242i has negative refractive power.

Baffle plate 250 and quarter phase plate 202c separate beam splitter cube 220 from wafer optical group 240. The baffle plate 250 is adjacent to the beam splitter cube 220 and the quarter phase plate 202c. The quarter phase plate 202c is adjacent to the lens 242a and the baffle plate 250 of the wafer optical group 240.

The beam splitter cube 220 includes a first prism 221 and a second prism 222 as shown in FIG. 2A. The first prism 221 is adjacent to the second prism 222. In addition, the first prism 221 is adjacent to the quarter phase plate 202b and the reticle lens 203. On the other hand, the second prism 222 is adjacent to the quarter phase plate 202d and the baffle plate 250. The first prism 221 includes a first optical surface 280a. The second prism 222 includes a second optical surface 280b. The first optical surface 280a is adjacent to the second optical surface 280b.

In one embodiment of the invention, one function of the reticle optical group 210 is to first process the light beam. The image pattern formed on the reticle 201 is an image pattern to be formed on the semiconductor wafer 241. Reticle optical group 210 focuses, magnifies and / or aligns light incident through reticle 201.

Beam splitter cube 220 is a polarization mirror. Thus, light having the same polarity as the beam splitter cube 220 passes through the beam splitter cube, but light with different polarities is reflected in the beam splitter cube. Further, if the light has the same polarity as the quarter phase plate 202 (a, b, c, d), the light may be incident on the beam splitter cube 220 and exit. Since the beam splitter cube includes a first prism 221 adjacent to the second prism 222, light is directed to the aspherical mirror optical group 230 by Snell's Law (ie, the angle of incidence is equal to the angle of reflection). Is reflected directly.

Aspheric mirror 231 increases the size of the input image reflected by beam splitter cube 220. The quarter phase plate 202b disposed in the optical path between the aspheric mirror 231 and the beam splitter cube 220 reverses the polarity of the light carrying the input image reflected by the beam splitter cube 220. Because of the change in polarity, light enters and passes through beam splitter cube 220. Aspheric mirror 231 performs these tasks as well as any other potential tasks in a manner known to those skilled in the art.

Folding mirror 225 receives light reflected by aspherical mirror 231 and passing through beam splitter cube 220. The quarter phase plate 202d disposed in the optical path between the folding mirror 225 and the beam splitter cube 220 reverses the polarity of the light and reflects the light back to the beam splitter cube 220. In one embodiment, the folding mirror 225 is a flat mirror without any optical power. In another embodiment, the folding mirror 225 has optical power and also magnifies and / or aligns the light coming from the beam splitter cube 220.

The baffle plate 250 prevents light from leaking through the beam splitter cube 220. Light incident on beam splitter cube 220 is reflected by many optical surfaces (eg, first optical surface 280a and second optical surface 280b) within beam splitter cube 220. Light reflects along any optical axis. However, some light is scattered through the beam splitter cube 220 and is not reflected along the optical axis. This produces background scattered light that causes distortion in image formation in the semiconductor wafer 241. The baffle plate 250 absorbs, filters, blocks or prevents this background scattered light. The baffle plate 250 prevents background scattered light from causing distortion in image formation in the semiconductor wafer 242. Baffle plate 250 absorbs any background scattered light generated from internal reflection within beam splitter cube 220. Two images are baffle plate 250 when light is reflected by various optical surfaces (eg, first optical surface 280a, second optical surface 280b, and the like) in reflective refraction system 200. Is formed. The first image is a condensed image of the image pattern formed on the reticle 201. The second image is a diffuse image (generated by background scattered light) of the image pattern formed on the reticle 201. The condensed image is the desired image and the diffuse image is the undesirable image. Therefore, to prevent image distortion on the semiconductor wafer 241, the baffle plate 250 absorbs the diffused image and delivers the focused image to the wafer group 240. In one embodiment, the baffle plate 250 is made of any known material capable of absorbing light.

4 shows a baffle plate having an opening 251. The opening 251 passes through a light beam that delivers a focused image of the pattern formed on the reticle 201. The size, shape and location of the openings 251 on the baffle plate 250 are specified by the application. In addition, the size and shape of the baffle plate 250 is also specified by the application. Baffle plate 250 may be made of any metal, plastic, or any other material capable of absorbing, filtering, blocking, or preventing background scattered light of substantially any wavelength. Those skilled in the art will appreciate that other embodiments of the baffle plate 250 are possible. In another embodiment, the size of the opening 252 is 30 mm x 26 mm.

Returning back to FIG. 2A, the reflective refraction system 200 of this embodiment has a reticle group 210, beam splitter cube 220, and wafer group 240 on the same optical axis 271. This affects the final image formed on the semiconductor wafer 241. In addition, since these optical groups are located on the same optical axis 271, the light from the reticle 210 is not reflected by the beam splitter cube 220 and passes directly through the beam splitter cube 220 to the wafer optical group 240. Is likely to be delivered. Thus, this light includes background scattered light (described above) that creates distortion in the image formed on the semiconductor wafer 241. Therefore, the baffle plate 250 minimizes the amount of this background scattered light reaching the semiconductor wafer 241.

Wafer group 240 receives a focused image from beam splitter cube 220. In one embodiment, lenses 242 (a, b, ..., m) of wafer group 240 magnify and align the image. The lens 242 may have various refractive powers. The magnified and / or aligned light forms on the semiconductor wafer 241 the same pattern as the image pattern on the reticle 201.

b. Image path in beam splitter optics design without spacer plate

FIG. 3A illustrates the light beam path of the FIG. 2A embodiment of the reflective refraction system 200. In this embodiment, light enters through reticle 201 and passes through a group of reticles of lens 310. Light 301 is magnified, focused and / or aligned by a group of reticles of lens 310. The reticle optical group 210 of FIG. 2A includes a reticle group of the reticle 210 and the lens 310.

Next, light 301 is incident on the first prism 221 of the beam splitter cube 220. Beam splitter cube 220 reflects light 301. In particular, the first optical surface 280a of the first prism 221 reflects the light 301. Aspheric mirror optical group 230 receives reflected light 302. A quarter phase plate 202b (not shown in FIG. 3A) disposed in the optical path between the aspheric mirror 231 and the beam splitter cube 220 changes the polarization of the light 302. The optical object of aspherical optical group 230 also focuses, magnifies and / or aligns the light before aspheric mirror 231 reflects light 302.

After the polarization change, the polarized light 303 returns to the beam splitter cube 220. The optical object of aspheric mirror optical group 230 magnifies and / or aligns the image represented by polarized light 303 before light 303 enters beam splitter cube 220. Since light 303 and beam splitter cube 220 have the same polarity, polarized light 303 passes through beam splitter cube 220.

Folding mirror 225 receives polarized and focused light 303 and reflects the light back to beam splitter cube 220. A quarter phase plate 202d (not shown in FIG. 3A) disposed in the optical path between the folding mirror 225 and the beam splitter cube 220 reverses the polarity of the light 303 and polarizes the light. Reflected as 304. The polarized light 304 has the same polarity as the second prism 222 of the beam splitter cube 220. The second prism 222 reflects light 304 towards the wafer group 340 and the semiconductor wafer 241. In particular, the second optical surface 280b of the second prism 222 reflects the light 304. Light beam 304 becomes light beam 305.

After being reflected by the second prism 222, light 305 passes through the baffle plate 250. Light 305 forms an intermediate image 299 (shown in FIG. 2A). The intermediate image 299 is formed before light 305 passes through the baffle plate 250. The light beam 305 delivers a condensed image and a diffuse image of the reticle 201 image pattern. After passing through the baffle plate 250, the baffle plate 250 passes through the light 306 which removes the diffused image and conveys the focused image. The baffle plate 250 absorbs any background scattered light in the beam splitter cube 220.

Light 306 passes through wafer optical group 340 and is further focused, magnified and / or aligned by an optical object within wafer optical group 340. Light beam 306 becomes focused, magnified, and / or aligned light beam 307. Focused, magnified and / or aligned light 307 forms an image pattern on semiconductor wafer 241. The image pattern on the semiconductor wafer 241 is the same as the image pattern formed on the reticle 201.

The advantage of this design is that the optical objects of the refraction system 200 (ie, reticle optical group 210, beam splitter cube 220, aspheric mirror optical group 230, etc.) reflect light evenly. This eliminates the possibility of image mirroring. Initially, first prism 221 reflects light passing through reticle 201. Aspheric mirror 231 secondly reflects light and directs the light through beam splitter cube 220 to folding mirror 225. The folding mirror 225 third reflects light to the second prism 222 of the beam splitter cube 220. Second prism 222 fourthly reflects light to wafer optical group 340 and semiconductor wafer 241. Since light is reflected evenly, the image pattern formed on the semiconductor wafer 241 is not mirrored.

c. Beam Splitter Optics Design with Spacer Plate

2B illustrates another embodiment of a reflective refraction system 200. 2B shows a reticle optical group 210, an aspheric mirror optical group 230, a beam splitter cube 220, a folding mirror 225, a baffle plate 250, and a wafer optical group 240 and a quarter phase plate. (202 (a, b, c, d)) is shown. The components and functions of the reticle group 210, the aspheric mirror optical group 230, the folding mirror 250, and the wafer optical group 240 are similar to the embodiment of FIG. 2A.

Returning to FIG. 2B, the beam splitter cube 220 includes a first prism 221, a spacer plate 223, and a second prism 222. The spacer plate 223 separates the first prism 221 and the second prism 222. The reticle group 210 is adjacent to the first prism 221. The reticle group lens 203 is adjacent to the first prism 221. Aspheric mirror optical group 230 is adjacent to first prism 221. Folding mirror 225 is adjacent to second prism 222. The baffle plate 250 is adjacent to the spacer plate 223. Wafer optical group 240 is adjacent to second prism 222. In one embodiment, the spacer plate 223 may be made of the same optical material as the first prism 221 and the second prism 222.

Spacer plate 223 creates an offset between axis 272a of reticle optical group 210 and axis 272b of wafer optical group 240. Compared with FIG. 2A, there is no single axis 271 for the reticle optical group 210 and the wafer optical group 240. Therefore, the spacer plate 223 removes some of the background scattered light in the beam splitter cube 220.

Spacer plate 223 also has two separate beam splitter surfaces 281a, 281b. The first beam splitter surface 281a is in the first prism 221. The second beam splitter surface 281b is in the second prism 222. The first beam splitter surface 281a of the spacer plate 223 is not adjacent to the second beam splitter surface 281b of the spacer plate 223. This is different from the embodiment of FIG. 2A where the first optical surface 280a is adjacent to the second optical surface 280b. In FIG. 2B, light reflects off two different surfaces within the beam splitter cube 220. This is different from the FIG. 2A embodiment where light reflects off the first optical surface 280a and the second optical surface 280b.

Since the spacer plate 223 creates an offset between the reticle optical axis 272a and the wafer optical axis 272b, light travels from the reticle optical group 210 through the beam splitter cube 220 to the wafer optical group 240. When transmitted directly, it helps to prevent the generation of background scattered light. The width of the spacer plate 223 may be varied or predetermined depending on the amount of light allowed to be transmitted from the reticle optical group 210 to the wafer optical group 240 through the beam splitter cube 220. Thus, the wider the spacer plate 223 is, the less light is allowed to pass directly through the beam splitter cube 220 without reflecting the optical surface within the beam splitter cube 220. The narrower the spacer plate 223 is, the more light is allowed to pass directly through the beam splitter cube 220. Thus, the width of the spacer plate 223 is specified depending on the application. That is, it depends on the amount of light desired by the designer to be transferred directly from the reticle optical group 210 to the wafer optical group 240 through the beam splitter cube 220.

Spacer plate 223 controls the amount of background scattered light that passes through beam splitter cube 220, but light from the reticle optical group generates additional background scattered light. Additional background scattered light is generated by internal reflection in the beam splitter cube 220. Because of the internal reflection in the beam splitter cube 220, the background scattered light forms a diffuse image in the baffle plate 250 before the light enters the wafer optical group 240 as described above.

In other embodiments, the spacer plate 223 may comprise a plurality of spacer plates. The plurality of spacer plates may have a multilayer configuration and may be made of an optical material similar to the first prism 221 and the second prism 222. In addition, the plurality of spacer plates can better correct birefringence. This embodiment produces a more coherent light beam reflected from the beam splitter cube 220 and ultimately produces an image on the wafer.

Therefore, the combination of the baffle plate 250 and the spacer plate 223 controls the amount of light passing directly through the beam splitter cube 220 and the background scattered light of the beam splitter cube 220 generated by internal reflection. Baffle plate 250 blocks any diffused image formed in baffle plate 250. The baffle plate 250 does not block the condensed image formed on the baffle plate.

In one embodiment, the folding mirror 225 is a flat mirror. In another embodiment, the folding mirror 225 has optical power. As with FIG. 2A, this focuses, aligns and / or enlarges light.

d. Image path of beam splitter optics design with spacer plate

3B illustrates the image path of the light beam of the FIG. 2B embodiment of the refraction refractive system 200. 3B shows a beam splitter cube 220 having a reticle 201, a reticle optic 301, a spacer plate 223, an aspheric mirror optical group 230, a folding mirror 225, a baffle plate 250, a wafer. The optical system 340 and the semiconductor wafer 241 are shown.

The light beam 301 enters the reflective refractive system 200 through the image pattern on the reticle 201 and passes through the reticle optics 310. Next, the light beam 301 is incident on the first prism 221 of the beam splitter cube 220. The first prism 221 reflects from the first beam splitter surface 281a to the aspherical mirror optical group 230. The light beam 301 becomes the reflected light beam 302.

Aspheric mirror optical group 230 focuses, magnifies and / or aligns light beam 302. Aspheric mirror 231 (not shown in FIG. 3B) reflects light beam 302. The quarter phase plate 202b (not shown in FIG. 3B) disposed in the optical path between the aspherical mirror 231 and the beam splitter cube 22 changes the polarization of the light 302. The light beam 302 becomes a polarized light beam 313.

Since the light beam 313 and the beam splitter cube 220 (including the first prism 221, the spacer plate 223, and the second prism 222) have the same polarity, the light beam 313 may be a beam splitter cube ( Pass through 220). After passing through the beam splitter cube 220, the folding mirror 225 reflects the light beam 313 back into the beam splitter cube 220. The quarter phase plate 202d (not shown in FIG. 3B) disposed in the optical path between the folding mirror 225 and the beam splitter cube 220 changes the polarization of the light beam 313. The light beam 313 becomes a polarized light beam 314.

Next, the light beam 314 is incident on the second prism 222 of the beam splitter cube 220. The second prism 222 reflects the light beam 314 from the second beam splitter surface 281b to the wafer optics 340. Light beam 314 becomes reflected light beam 315.

The light beam 315 represents a focused image or an intermediate image 299 (FIG. 2B) of an image pattern formed on the reticle 210. The intermediate image 299 is formed before the light beam 315 passes through the baffle plate 250 and enters the wafer group optics 340. The diffuse image is formed in the baffle plate 250. Background scattered light generated from the reflection inside beam splitter cube 220 results in the formation of a diffuse image. The baffle plate 250 blocks the diffuse image from entering the wafer group optics 340 and negatively affects the image on the semiconductor wafer 241.

Spacer plate 223 also creates an offset between reticle optical axis 272a and wafer optical axis 272b. Therefore, the light beam 301 is not transmitted to the wafer optical group 340 through the beam splitter cube 220 as in the embodiment shown in FIG. 2A.

Referring again to FIG. 3B, wafer optics 340 also magnify and / or align light beam 315. Light beam 315 becomes light beam 317. Light beam 317 represents a more focused and / or aligned focused image of the pattern on reticle 201. Next, the light beam 317 forms an image on the semiconductor wafer 241.

As with the design of FIG. 2A, the advantage of this design is that the optical objects of the refraction system 200 (ie, reticle optical group 210, beam splitter cube 220, aspheric mirror optical group 230, etc.) may even light. It is a reflection. This removes the possibility of image mirroring. The first prism 221 first reflects light passing through the reticle 201. Aspheric mirror 231 secondly reflects light and directs the light through beam splitter cube 220 to folding mirror 225. The folding mirror 225 third reflects light back to the second prism of the beam splitter cube 220. Second prism 222 fourthly reflects light to wafer optical group 340 and semiconductor wafer 241. Since light is reflected evenly, the image pattern formed on the semiconductor wafer 241 is not mirrored. In addition, because the spacer plate 223 is added to the beam splitter cube 220 in combination with the baffle plate 250, the amount of light leaking from the reticle optical group 210 through the beam splitter cube 220 is reduced.

4. Conclusion

Embodiments of the method, system, components of the invention have been described herein. These examples have been described for illustrative purposes only and are not intended to be limiting. Other embodiments are possible and covered by the present invention. Such embodiments will be apparent to those skilled in the relevant art based on the techniques included herein. Accordingly, the spirit and scope of the invention should not be limited by the above-described exemplary embodiments, but defined only by the following claims and their equivalents.

As described above, according to the present invention, an optical system design capable of generating an image that is not flipped (mirrored) on a semiconductor wafer can be provided.

Claims (23)

An optical system for projecting a pattern formed on a reticle onto a substrate, A beam splitter having a pair of prisms separated by a spacer plate; A group of reticle lenses positioned adjacent the first surface of the reticle and the beam splitter; An aspheric mirror optical group positioned adjacent to a second side of the beam splitter; A folding mirror optical group adjacent to the third side of the beam splitter and positioned opposite the aspheric mirror group; And A wafer optical group adjacent to the fourth side of the beam splitter and positioned opposite the reticle lens group, Light projected from the reticle through the reticle lens group is reflected by the beam splitter onto the aspheric mirror optical group, and is reflected by the beam splitter into the folding mirror optical group, and by the beam splitter the wafer optics Optical system that is reflected in groups. 2. The apparatus of claim 1, further comprising a baffle plate positioned adjacent the fourth side of the beam splitter and the wafer optical group, wherein the baffle plate is generated by internal reflection of light in the beam splitter. An optical system that prevents background scattered light from entering the wafer optical group. The optical system of claim 2, further comprising an intermediate image formed in the baffle plate when light is transmitted from the beam splitter to the wafer optical group. The optical system of claim 1, wherein the aspheric mirror optical group further comprises an aspheric mirror and a plurality of lenses positioned between the aspherical mirror and the beam splitter. The optical system of claim 1, wherein the wafer optical group further comprises a plurality of lenses positioned in an optical path between the beam splitter and a wafer. The optical system of claim 1 wherein the folding mirror optical group comprises a folding mirror having optical power. The optical system of claim 1, wherein the folding mirror optical group comprises a flat folding mirror. An optical system for projecting a pattern formed on a reticle onto a substrate, Reticle lenses; A beam splitter having a spacer plate separating the pair of prisms; Aspherical mirror; Folding mirror; And A wafer optical element, Light projected from the reticle through the reticle lens is reflected by the beam splitter to the aspheric mirror, reflected by the beam splitter to the folding mirror, and reflected by the beam splitter to the wafer optical element . 9. The apparatus of claim 8, further comprising a baffle plate positioned between the beam splitter and the wafer optical element, wherein the baffle plate directs background scattered light generated by internal reflection of light within the beam splitter to the wafer optical element. Optical system to prevent that. 10. The optical system of claim 9, wherein the baffle plate comprises an opague shield that reduces the effects of light deflecting on the system. The optical system of claim 8, further comprising a plurality of lenses positioned between the aspheric mirror and the beam splitter. The optical system of claim 8, wherein an offset generated by light passing through the beam splitter varies with the width of the spacer plate. In an optical system, a method of forming an image on a wafer plate by passing light through a beam splitter having a reticle and an optical prism portion separated by a spacer plate, the method comprising: (a) directing light to the beam splitter; (b) directing the polarized light back from the beam splitter to the aspherical mirror; (c) reflecting light from the aspheric mirror to a folding mirror, wherein light passes through a beam splitter optical prism portion and the spacer plate; (d) reflecting light back from the folding mirror to the beam splitter; And (e) transferring the light reflected by the folding mirror through the beam splitter to a wafer plate. In an optical system, a method of forming an image on a substrate by passing light through a beam splitter having a reticle and first and second prism halves separated by a spacer plate, the method comprising: (a) transferring light through the reticle and the first optical prism half to an aspherical mirror, where the light is reflected back to the beam splitter by the aspherical mirror; (b) after reflection by the aspherical mirror, transmitting light to the folding mirror through the first optical prism half, the spacer plate, and the second optical prism half, wherein the light is reflected by the folding mirror -; (c) after reflection by the folding mirror, transmitting light through the second optical prism half to the substrate. An optical system for projecting a pattern formed on a reticle onto a substrate, A beam splitter having a pair of prisms; A group of reticle lenses positioned adjacent the first surface of the reticle and the beam splitter; An aspheric mirror optical system positioned adjacent the second face of the beam splitter; A folding mirror optical system adjacent the third face of the beam splitter and positioned opposite the aspheric mirror optical system; And A wafer optical system adjacent the fourth side of the beam splitter and positioned opposite the reticle lens group, Light projected from the reticle through the group of reticle lenses is reflected by the beam splitter to the aspheric mirror optical system, reflected by the beam splitter to the folding mirror optical system, and by the beam splitter the wafer optical system Reflected by optical system. The optical system of claim 15, wherein the prism of the beam splitter cube is separated by a spacer plate. 16. The apparatus of claim 15, further comprising a baffle plate positioned adjacent to the fourth side of the beam splitter and the wafer optical system, wherein the baffle plate is a background scattered light generated by internal reflection of light in the beam splitter. Optical system for preventing entry into the wafer optical system. 18. The optical system of claim 17, further comprising an intermediate image formed in the baffle plate when light is transferred from the beam splitter to the wafer optical system. 16. The optical system of claim 15, wherein the aspherical mirror optical system further comprises an aspherical mirror and a plurality of lenses positioned between the aspherical mirror and the beam splitter. The optical system of claim 15, wherein the wafer optical system further comprises a plurality of lenses positioned in an optical path between the beam splitter and the wafer. 16. The optical system of claim 15, wherein the folding mirror optical system comprises a folding mirror having optical power. 16. The optical system of claim 15, wherein the folding mirror optical system comprises a flat folding mirror. In an optical system, a method of forming an image on a wafer optical element, the method comprising: (a) transmitting light through the reticle lens to the beam splitter, the beam splitter having an optical prism portion separated by a spacer plate; (b) reflecting light by the beam splitter to an aspherical mirror; (c) reflecting light reflected by the aspherical mirror through the beam splitter to a folding mirror; And (d) reflecting light reflected by the folding mirror through the beam splitter to the wafer optical element.

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